docs: def quick_plot(cmap, fname=None, fig=None, ax=None, N=10):
      '''Show quick test of a colormap.
  
      '''
  
      x = np.linspace(0, 10, N)
      X, _ = np.meshgrid(x, x)
  
      if ax is None:
          fig = plt.figure()
          ax = fig.add_subplot(111)
      mappable = ax.pcolor(X, cmap=cmap)
      ax.set_title(cmap.name, fontsize=14)
      ax.set_xticks([])
      ax.set_yticks([])
      plt.colorbar(mappable)
      plt.show()
  
      if fname is not None:
          plt.savefig(fname + '.png', bbox_inches='tight')